Tuning unit



July 25, 1950 v. H. AsKE 2,516,287

TUNING UNIT Filed May 12, 1948 IN V EN TOR. Vernon H. 14s/fe Hita/neg Patented vJuly 25,1950

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'f 'OFFICE' TUNING UNIT Vernon H. Aske, Huntington Station, N. Y., as-v signor to Sylvania Electric Products Inc., acorporation of Massachusetts Application May 12, 1948, Serial No. 26,651

Claims.

The present invention relates to tuning devices for high frequency radio circuits.

An object of the invention is to provide a novel compact and simple tuner adjustable over a wide frequency range and operable at frequencies of the order of 100 to 1,000 megacycles per second.

In accordance with the invention a self-supporting coil of one or more turns has an axial extension carrying a stationary condenser plate, and a metallic plug is supported for axial travel between extreme positions, within the coil and adjacent 4the condenser plate, respectively.

The following detailed disclosure of two illustrative embodiments of the invention will aid in a fuller appreciation of the invention and of its further objects and features of novelty. In the drawings:

Fig. 1 is a perspective view of a tuner embodying the invention, having a single-turn coil;

Fig. 2 is a lateral view of another novel form of tuner, having a one-and-a-half turn coil; and

Fig. 3 is a plan View of a sheet metal blank adapted to be formed into both the coil and the stationary condenser plate of the tuner in Figs. 1 and 2.

Referring now to Fig. l, circular plate IIJ is shown carried by axial strip I2 on one end I4 of a circular one-turn coil I6 the other end I8 of which is carried by angled arms 20 and 22 which constitute a mounting bracket. The parts described can be formed from a single piece of sheet metal cut to the shape in Fig. 3 and subsequently bent into the configuration shown in Fig. l. This coil-andcondenserplate structure is adapted to be secured to a supporting panel by externally threaded sleeve 24 and retaining nut 26, the panel being suitably apertured to admit the sleeve. A tuning plug 28 of brass is carried by a rod 30 having its bearing within sleeve 24, and is adapted to move between extreme positions, either adjacent plate I0 or Within coil I6. The adjustment is effected by virtue of external threads on shaft 30 and threads within sleeve 24, in the form shown, although it is feasible to support tuning plug 28 in a slide bearing for endwise adjustment by any other suitable mechanism such as is commonly found in push-button tuners.

When plug 28 is adjacent plate II) there is a maximum of capacity associated with the tuner, and the inductance is a maximum. When plug 28 is withdrawn from plate IIJ into coil I6 the capacity of plug 28 and plate I0 as a two-plate condenser is reduced, and the inductance of coil l g"; length of arm 20,

I 6 is also reduced. Plug28 acts as a short-circuited secondary winding reflecting capacity into coil I6` as avprimary winding. There is a certain inherent capacity between the plug and the coil, which capacity is partly' sustained as the plug leaves the coil by the'proximityof plug 28 to arm I2. Where sleeve 24 and shaft 3U are of metal the tuner is useful as a parallel-resonant circuit with arm 22 as one terminal and point lI4 or arm I2 as the opposite terminal. Coupling between this impedance and a vlower-impedance line is effected by making connections to arm 22 anda tap along coil I B determined empirically, or by an adjustable capacitive plate outside plate Il). Ordinarily the panel to which arm 22 is secured is a grounded chassis.

By adjusting principally the diameter of the coil, the diameter and length of the plug, and the sizes of plate I0 and arm I2, the center frequency and frequency range of the tuner in Fig. 1 can be widely varied. The following dimensions will be found to yield a parallel-resonant tuner having a substantially linear frequencydisplacement characteristic between 500 and 650 megacycles per second; plug 28, T76 diameter; arm I2, 1A long; plate I, 1/2 diameter; length of strip between points ld and i8, 11-9; axial length of plug 28, 1A3; width of strip in coil I6, IAQ. The merit factor, Q, of the tuner thus constructed is remarkably constant over the tuning range, and is of the order of for silver-plated parts.

In the form of tuner shown in Fig. 2, coil I6 has one and a half helical turns in place of the single circular turn in Fig. 1. Arm I2 and tuning plug 28 are axially extended for more complete coupling of the plug to the coil when the plug is positioned within that coil. With dimensions otherwise substantially equal to the tuner in Fig. 1, the tuner of Fig. 2 operates over a range of from 350 to 500 megacycles per second. Coil I6 and stationary condenser plate I are adapted to be formed from a single piece of sheet metal formed essentially as in Fig. 3, with the length of strip portions I2 and I 6 properly adjusted.

Various detailed modifications of the forms disclosed above will occur to those skilled in the art. Therefore I desire the appended claims to be given broad interpretation, consistent with the spirit of the invention.

What is claimed is:

l. A tuner comprising a self-supporting electrically conductive cylindrical coil, an electrically conductive axial arm extending from said coil,

metal tuning plug connected to the other end.

of said coil to adjust the frequency of said tuner from a lower limit with the plug adjacent said stationary plate and an upper-limitwithL said plug spaced from said plate and-within said coil.

3. A high-frequency tuner comprising a metallic I bracket, a metallic sleeve secured to.v one. armi. of said bracket, a metallic cylindrical coil extending from the other arm of said bracket, a metallic arm extending from thegopposte end of said coil, @metallic plate ext-,enclins acrcssthaaxisof sai-.d ce' and, iQ 'mics etatllenaryY Gentlemen plate.

t inclus ardeisfieed; alone the. axis ca-said plus: from nositicn withint the,

5. A tuner comprising a self supporting coil and condenser plate formed of a single piece of sheet metal, said piece including a strip of metal curved about an axis to constitute said coil and short lengths of metal extending laterally from the ends of said strip in opposite directions parallel to said axis, said short lengths having bent portions extending acrossl thejaxis of said coil, one of said portions constituting a support and the other being enlarged to constitute a condenser plate, said tuner additionally including a metallic tuning plug, a metallic rod joined to said plug, and a rod bearing determining predetermined travel of said plugl axially of said coil and with variable. spacing from said condenser plate.

VERNON H. ASKE.

REFERENCES CITED The following references are of record in the fuer-Qi Patenti UNITED. STATES PATENTS..

Number i Name Date.

2.2225770 Hartl'if-.f-T---e-u- NOV; 2,6; 194,0, 2,394,391 Martowcz I Feb, 194;@ 2,403,349 I )olberg` July 2; 12,46 2,46761-3-7 Germer Apr 1 9; 1.794,9A 2,471,705 schmitt Mayet; 194ev @THER REFERENCES f RadiorCraft for-1 June 1&45., by I.A Queen,` on

v pages 5.6.0` and 596.. 

